FPGA implementation of a three-level power amplifier for magnetic bearings

Three-level pulse width modulation (PWM) scheme is recommended for switching power amplifiers used in digitally controlled active magnetic bearings (AMB) because it allows the amplifier to work at a low switching frequency with relatively low current harmonics. In one four-axis AMB there are usually more than ten switching devices to be controlled. Therefore FPGA is a good platform for the implementation of three-level PWM. A three-level PWM scheme used on h-bridge power amplifiers for AMBs is presented. The FPGA solution for that three-level scheme is given in detail. The setup and results of the test experiment with a digital power amplifier board featured a XC3S1000 FPGA are presented. The results show that the four-channel current control task together with the corresponding modulation task can be carried out by one FPGA at a low cost of resources.